High reliability electronic equipment, including fault-tolerant computer systems, have become increasingly popular due to the increased costs resulting from equipment failures. Also, fault tolerant electronic systems having redundant elements have dropped in cost because of decreasing equipment costs. By way of example, computer processor and memory costs have decreased significantly in recent years for equivalent performance.
Although the reliability of electronic systems, including computer systems, has increased, many equipment failures occur because of failures in the power supply system. Although there do exist improved reliability power supply systems having redundant elements, these systems possess many shortcomings and lack many desirable features. For example, many power supply systems now in use fail to provide sufficient redundancy so that a total power failure occurs when one of several key components fail. Although some of such subsystems utilize a battery backup in the event A.C. power is lost, the backup supplies power to only some of the components of the system such as the computer memory. Even though the memory is powered, an orderly shutdown of the computer is prevented, resulting in a loss of data.
The present power supply system overcomes the above-noted shortcoming. Redundancy of all major components is provided so that almost no single failure will result in a power loss. In the event an A.C. power loss occurs, a battery backup is provided which is capable of maintaining power for sufficient time to permit, for example, an orderly shutdown of a computer powered by the system. In addition, the subject power system includes monitoring capabilities for monitoring many vital functions of the system and command apparatus for commanding certain components of the system to predetermined states. The subject system also facilitates the diagnosis of component failures and enhances the serviceability of the equipment. These and other advantages of the subject power system will become apparent to those skilled in the art, upon reading the following Best Mode for Carrying Out the Invention, together with the drawings.